Can I get a transit visa on arrival?

Hi. My name is Xavier Symons and I am taking a group of 7 high school students on a service project to Vietnam. We are building houses in a poor village outside of Saigon. We are flying China Southern Airlines to Vietnam, and have two transit stops -- one in Guangzhou and another in Beijing. We have only just been told that we will need a visa to travel from Guangzhou to Beijing. I'm actually on the plane now. Do you have any suggestions about what I can do when I get to Guangzhou? Any advice would be greatly appreciated.